Imagine a physician who treats cancer patients by checking for excessive ear wax, and you have some idea of how ethics enforcement works in Washington.

Last week we had a perfect illustration when the Office of Congressional Ethics cleared Rep. Spencer Bachus, R-Ala., of alleged insider-trading violations arising from the financial meltdown of 2008.

In his capacity as chairman of the House Financial Services Committee, Bachus had attended a private meeting with then-Treasury Secretary Henry M. Paulson Jr. and Federal Reserve Chairman Ben S. Bernanke. The next day, using options, he bet that stocks would fall.

Now, a member of Congress ought to be smart enough not to make such trades, which look really bad. Eventually there was a big stink in the media and an official probe. Yet Bachus didn’t break any laws, and his profit of $5,715 was laughable.

But what if I told you that in the 2010 election cycle Bachus and his political action committee got nearly $1.4 million from the very financial services industry he’s supposed to oversee as committee chairman?

Sounds outrageous, doesn’t it? Yet there are no ethics investigations. Nobody even seems to bat an eye.

That’s because this is business as usual in Washington, where the most appalling stuff is done right out in the open.

You’d think, for example, that public servants oughtn’t to take money from those they regulate. But the nonprofit Citizens for Responsibility and Ethics in Washington found that, in the 2010 election cycle, financial services supplied 64 percent of the money given to the Bachus campaign and his PAC.

Consider also that in the 1998 election cycle, when Bachus was just a member of the committee, he got $192,685 from the industry. For the 2010 election, by which time he was chairman, those donations were up 620 percent.

Did I mention that Bachus ran unopposed in 2010? He hasn’t had anyone run against him in his heavily Republican district since 2002.

The remarkable thing is that the campaign finance record of Spencer Bachus isn’t especially egregious for a committee chair. The point is not that he’s unusual — it’s that he’s typical. Nearly everyone in Congress is focused on raising money, and many of the people writing the checks expect that they’re buying influence. In general, they’re probably right.

Under the circumstances, it’s absurd to think Congress would put the interests of the people first. Its members are just too dependent on special-interest money.

This is a tough problem. Campaign finance limits haven’t worked very well, and the Supreme Court’s decision in the Citizens United case has opened the floodgates to corporate and union money.

I honestly don’t have the answer, but one interesting proposal, from the legal scholars Bruce Ackerman and Ian Ayres, offers a fresh approach by emphasizing more money instead of less.

They want every American voter to be given a $50 “democracy voucher” good for a federal campaign donation. Candidates would only be eligible to receive these donations if they forswear other money except for contributions from citizens, capped at $100 each.

Candidates would have a strong incentive to participate because the system would make available more than $6 billion — triple what was spent in the 2010 election cycle. We’d save more than that by reducing the power of special interests to extract tax breaks and other goodies.

Will it really work? I don’t know, but I’m open to any ideas that will stem the corrupting tide of money without limiting freedom of speech.

Daniel Akst is a columnist for Newsday and a member of the newspaper’s editorial board.